To solve your issue pls update MB BIOS to "BIOS Version 5559 - SOX5810J.86A.5559.2011.0405.2144"
To understand detail reasons and soulutions for your issue pls read below document......
Thank you for your response.
As you correctly guessed, The issue was in the BIOS, and I actually installed the update on 2-28-2011.
Due to the age of the original BIOS, Intel tech support recommended 3 intermediate BIOS upgrades rather than a single push to the latest.
Things have been working very well since then.
My apologies for not returning and updating this thread indicating i had the solution, and thus wasting your time.